两封信随机地投入标号为1，2，3，4的4个邮筒，则1，2号邮筒各有

【名词&注释】

近代中国(modern china)、中国社会(chinese society)、晶体渗透压(crystalloid osmotic pressure)、胶体渗透压(colloid osmotic pressure)、反帝反封建、中共二大(second national congress of the party)、民主革命纲领、半殖民地半封建、中共一大(the first conference of the cpc)、碳酸氢盐(bicarbonate)

[单选题]两封信随机地投入标号为1，2，3，4的4个邮筒，则1，2号邮筒各有一封信的概率等于

C.

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学习资料：

[单选题]在近代中国，首次提出彻底的反帝反封建的民主革命纲领的是（　　）

A. 《民报》发刊词
B. 兴中会誓词
C. 中共一大^{(the first conference of the cpc)}
D. 中共二大

[单选题]

[单选题]We had a long telephone________yesterday evening．

A. dialogue
B. conversation
C. talk
D. speech

[单选题]The reason why all the solar energy falling on the earth can’t be utilized is that ______．

根据以下内容，回答下面的题目。The energy which the sun radiates goes in every direction, and only a minute part of it falls on the earth．Even so, it represents power of about 5,000,000 horsepower (马力) per square mile per day; the sun gives us as much energy every miunte as mankind utilizes in a year．At present, we use this energy indirectly, and it is our final source of power．Coal represents the chemical action of the sun on green plants thousands of years ago．Water power results from the rain formed by vapor which comes from the evaporation of water under the sunshine．Even windmills operate because of air currents set in motion by the different heating affects of the sun in different places．Some day, through chemistry or some type of solar engine, we shall harness this great source of energy more directly．Already a scientist has worked out an engine, surprisingly efficient, in which the sun’s rays are concentrated through mirrors on a tube of water to create steam．How much energy given off by the sun reaches the earth?

A. only a very small part is available
B. the sun is too distant from the earth
C. it takes thousands of years for this energy to be stored up in coal and oil
D. our scientific knowledge is not sufficient

[单选题]Although he had stayed in that business for two years，_______he still wanted to switch to a different career．

A. and
B. but
C. yet
D. So

[单选题]_______it is to listen to music!

A. What fun
B. How a fun
C. What a fun
D. How fun

[多选题]维护血管内外和细胞内外水平衡的主要因素是（　　）

A. 血浆中碳酸氢盐^{(bicarbonate)}浓度
B. 血浆与组织液的晶体渗透压
C. 血浆Ca2+浓度
D. 血浆中O2和CO2浓度
E. 血浆与组织液的胶体渗透压

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